Simultaneous vision emulation for fitting of corrective multifocal contact lenses

ABSTRACT

An emulator including a beam splitter for splitting incoming light energy into a first component directed along a first optical path, and a second component directed along a second optical path distinct from the first optical path. The emulator includes a first receptacle positioned to pass light energy directed along only the first optical path. The first receptacle is capable of receiving an add lens for providing an add power. A beam combiner is positioned to combine light energy of the second component with light energy of the first component that has passed the first receptacle, i.e. to have the add power applied, and to direct the combined light energy along a common optical path. Additional receptacles are provided that are capable of receiving a sphere and/or a cylindrical lens in position to pass the combined light energy traveling along the common optical path.

FIELD OF THE INVENTION

The present invention relates generally to corrective lenses forenhancing visual acuity, and more particularly to methods and devicesfor fitting of corrective multifocal contact lenses.

DISCUSSION OF RELATED ART

Current popular clinical methodology for fitting a person withcorrective lenses involves development of a vision prescription using aphoropter. Typically, an optometrist or other health care professionalhas the person (patient) look through the phoropter to view a chartdisplayed at a distance. The health care professional then uses thephoropter to introduce into the person's sight path various lenses, orcombinations of lenses, to determine the optimal add, sphere and/orcylinder parameters of a corrective lens prescription for the person.This typically involves having to ask the person to compare the visualacuity from various combinations of lenses and report which combinationprovides the clearest appearance of text on the chart. Custom fittedeyewear can then be manufactured for the person according to theprescription thus obtained.

This approach is suitable for single vision and mono-vision eyeglassesor contact lenses. This approach is also suitable for multifocalspectacle lenses as a person can manipulate the eye or pupil toselectively focus on an object through different parts of a multifocalspectacle lens having areas characterized by different focal lengths.This approach, however, has proven inadequate for multifocal contactlenses because such contact lenses have a principle of operationdifferent from that of the corrective eyewear mentioned above.

In particular, most multifocal contact lenses made from soft lensmaterials operate on a principle of “simultaneous vision.” Likemultifocal spectacle lenses, multifocal contact lenses have differentareas with different focal lengths, one optical power for distancevision and the other for near vision. Accordingly, the focal powervaries over the areas of the multifocal contact lens. Unlike multifocalspectacle lenses, however, both of these areas of different focallengths in multifocal contact lenses are positioned on a wearer's eyeover the pupil and thus the wearer cannot selectively focus throughdifferent parts of the lens. Instead, multiple images of various degreesof sharpness, corresponding to the focal power of each area of the lens,are focused simultaneously on the retina of the wearer's eye (the“simultaneous vision effect”). It is believed that the human brainseparates, combines or otherwise processes these images so that theindividual perceives a single, satisfactorily clear image.

Phoropters cannot emulate this simultaneous vision effect and thus arenot suitable or optimal for fitting multifocal contact lenses. As aresult, a person is usually fitted with multifocal contact lenses byfirst obtaining a vision prescription using a phoropter, dispensingmultifocal contact lenses meeting that prescription, then testing theperson's vision while wearing those multifocal contact lenses.Typically, the person reports less than optimal visual acuity, and atrial-and-error approach follows in which the person is fitted withadditional sets of multifocal contact lenses until satisfactory visualacuity is reported. This iterative process is frustrating and timeconsuming as it typically takes 15–45 minutes for each set of contactlenses to properly center on the eyes, to become suitably wet, and tootherwise settle before testing for visual acuity. This lengthy processis costly for health care professionals, and such costs are compoundedby the need to discard one or more sets of rejected multifocal contactlenses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a simultaneous vision emulator inaccordance with the present invention.

FIGS. 2A and 2B are front and rear perspective views of an exemplarysimultaneous vision emulator device in accordance with the presentinvention.

FIG. 2C is a cross-sectional perspective view of the device of FIG. 2B,taken along line 2C—2C of FIG. 2B.

FIG. 3 is a perspective view of an exemplary lens for use with thedevice of FIGS. 2A–2C.

FIGS. 4A and 4B are rear and front perspective views of an alternativeembodiment of the device of FIGS. 2A–2C.

FIG. 4C is a cross-sectional perspective view of the device of FIGS. 4Aand 4B, taken along line 4C—4C of FIG. 4B.

FIG. 5 is a perspective view of an alternative embodiment of the deviceof FIGS. 4A–4C.

FIG. 6 is a top view of the device of FIG. 5, with portions removed forillustrative clarity.

FIG. 7 is a schematic diagram illustrating a convergence feature of thedevice of FIG. 6.

FIG. 8 is a perspective view of another alternative embodiment of thedevice of FIGS. 4A–4C.

FIG. 9 is a flow diagram illustrating a method for emulating amultifocal contact lens to produce a simultaneous vision effect on aretina of an eye in accordance with the present invention.

FIG. 10 is a schematic diagram of another simultaneous vision emulatorin accordance with the present invention.

DETAILED DESCRIPTION

The present invention provides a device and method that can be usedduring fitting of a patient for multifocal contact lenses to emulate amultifocal contact lens by producing a simultaneous vision effect on aretina of an eye. In this manner, the inaccuracies relating todevelopment of a prescription using a phoropter, which does not operateon a simultaneous vision principle, and the resulting waste of time andmoney for trial-and-error based prescription tuning can be eliminated.Accordingly, an accurate multifocal contact lens prescription may beobtained without the need to place any contact lenses on the eyes.

The invention provides an emulator that can be used during fitting of aperson for multifocal contact lenses to emulate a multifocal contactlens by producing a simultaneous vision effect on a retina of an eye. Anemulator device in accordance with the present invention includes a beamsplitter positioned to split incoming light energy into a firstcomponent directed along a first optical path, and a second componentdirected along a second optical path distinct from the first opticalpath. The device further includes a first receptacle positioned to passlight energy directed along only the first optical path. The firstreceptacle is capable of receiving an add lens for providing an addpower. A beam combiner is positioned to combine light energy of thesecond component with light energy of the first component that haspassed the first receptacle, i.e. to have the add power applied, and todirect the combined light energy along a common optical path. Second andthird receptacles are provided which are capable of receiving a spherelens and/or a cylindrical lens. These receptacles are provided inposition to pass the combined light energy traveling along the commonoptical path.

In this manner, the emulator disperses incoming light energy along twodistinct paths, applies an add power to one of the paths, and a sphereand/or cylindrical power to combined light energy from the two distinctpaths. This creates a near image, i.e. an image that is in focus at arelatively near position, and a distance image, i.e. an image that is infocus at a relatively distant position. Both images are simultaneouslyfocused on a retina of an eye of a person looking through the emulator,thereby creating a simultaneous vision effect comparable to that createdby a multifocal contact lens.

The emulator device may include two oculars, each ocular including theoptics discussed above. The device may further include an interpupillarydistance mechanism for adjusting a distance between the ocular foralignment with variously spaced pupils, and a convergence mechanismcapable of rotating the oculars to cause sight/optical pathstherethrough to converge at a near point. This simulates a readingcondition in which the human eyes pivot inwardly to focus at a pointrelatively near the face.

A method for emulating a multifocal contact lens to produce asimultaneous vision effect on a retina of an eye is also provided.

Referring now to FIG. 1, a schematic diagram illustrates how incominglight energy is manipulated to emulate simultaneous vision in accordancewith the present invention. Such incoming light energy may be ambientlighting in an optometrist's office, such as that reflected from aconventional eye chart viewed by a person during the eye examinationprocedure. Such light energy is typically non-polarized polarized, asshown at A in FIG. 1. It will be appreciated that FIG. 1 includes a raytrace model for illustrative purposes.

In this example, though optional, such incoming light energy A is firstpassed through a polarizer 10, e.g. an absorption polarizer, whichreceives incoming non-polarized or randomly polarized light and providesan output of linearly polarized light oriented at an angle relative to areference plane. The linearly polarized light travels an optical path Xinto a beam splitter 12. The beam splitter 12 is positioned to splitincoming light energy into a first component A′ having a firstpolarization (the “S” polarization), and a second component A″ having asecond polarization (the “P” polarization). It should be noted that a50%/50% ratio between the two polarizations is assumed with randomlypolarized scene lighting. The absorption polarizer 10 can be used toensure a 50%/50% ratio by mounting the polarizer at 45 degrees relativeto a reference plane/the beam splitter 12. This ratio is presentlybelieved to be advantageous. Alternatively, the polarizer can beoriented at other angular orientations to tune the intensity ratiobetween the S and P polarized components exiting the beam splitter 12.Optionally, a cube polarizer or similar component may be used instead ofthe absorption polarizer 10.

The beam splitter 12 directs the first and second components along twodistinct optical paths, namely, an S path for near vision, and a P pathfor distance vision. By way of example, the beam splitter 12 may be avisible waveband cube splitter, or a visible waveband cube polarizer.Such optical components are well known in the art. It should be noted,however, that use of the cube splitter tends to transmit some lightenergy that would otherwise be reflected with a cube polarizer, therebyresulting in a dimmer appearance of a viewed image.

In accordance with the present invention, one of the components ispassed through an add lens. In the example of FIG. 1, the firstcomponent A′ is passed through add lens 16, which is positioned to passlight energy traveling the S path. The add lens 16, in cooperation withthe sphere lens 22 discussed below, focuses the first component's lightenergy for near viewing. This add lens may be selectively interchangeduntil the person reports satisfactory visual acuity, as discussedfurther below. The second component A″ is not passed through the addlens.

The first component A′, as refracted by the add lens 16, and the secondcomponent A″ are then directed into a beam combiner 20 positioned tocombine the first and second components A′, A″ and direct them along acommon optical path Y. By way of example, the beam combiner 20 may be avisible waveband cube splitter, or a visible waveband cube polarizer, asdiscussed above with respect to the beam splitter 12. The beam splitter12 and beam combiner 20 need to be properly oriented to achieve thedesired effect described above, as will be appreciated by those skilledin the art.

In the example of FIG. 1, reflectors 14, 18, such as total internalreflection (TIR) fold prisms 14, 18 functioning in TIR mode, arepositioned to direct the first component A′ of the light energy from thebeam splitter 12, through the add lens 16, and to the beam combiner 20,as shown in FIG. 1. Accordingly, the reflectors 14, 18 help to definethe S path. This provides for physical separation of the first andsecond components A′, A″ to allow space for insertion of an add lens inthe optical path (S path) of the first component A′ and withoutinterfering with the optical path (P path) of the second component A″.Alternatively, a front surface or rear surface mirror could be used asreflectors 14, 18 in place of the prisms to direct the first componentA′ along an S path in a similar manner.

The combined light energy A′A″ exiting the beam combiner 20 travels acommon path and then passes through a sphere lens 22 and/or acylindrical lens 24 of the emulator before it enters the person's cornea26 a and lens 26 b and is projected onto the retina 26 c of the humaneye 26. The sphere lens 22 focuses the combined light energy fordistance vision. The cylinder lens corrects for astigmatism. The sphereand cylindrical lenses 22, 24 may be selectively interchanged until theperson reports satisfactory visual acuity, as discussed further below.Accordingly, when a person views the typical eye chart through theemulator, a near image (from the S path) and a distance image (from theP path) are simultaneously presented on the person's retina 26 c toprovide the simultaneous vision effect. Accordingly, a visionprescription obtained using the add, sphere and/or cylinder parametersof the add, sphere and/or cylindrical lenses 16, 22, 24 providingsatisfactory visual acuity will be accurate for use to prescribemultifocal contact lenses, negating the need for trial-and-errortesting.

Preferably, a device for emulating simultaneous vision includes two setsof the optical components discussed above with respect to FIG. 1,namely, one set for each eye. Each set is referred to herein as anocular. In this manner, if desired, both eyes may be used in viewing thechart and developing a vision prescription. Accordingly, the device is astereoscopic emulation device. It should be noted that an occluding lensmay be inserted in one ocular to allow viewing with only one eye, evenwhen the device includes two oculars.

FIGS. 2A, 2B and 2C are front, rear and cross-sectional perspectiveviews of an exemplary simultaneous vision emulator device 50 inaccordance with the present invention. This emulator device 50 includestwo oculars, each having optics discussed above with reference toFIG. 1. As shown in FIGS. 2A–2C, the device 50 includes a housing 52having front 54 and rear 56 ends. For illustrative purposes, a portionof the housing 52 is shown removed in FIGS. 2A–2C. Referring now toFIGS. 1 and 2A–2C, the housing 52 supports a polarizer 10, e.g. anabsorption polarizer, for linearly polarizing incoming light energy, asdiscussed above with reference to FIG. 1. In the example of FIGS. 2A–2C,the absorption polarizer 10 is fixedly mounted at a 45 degree angle withrespect to the beam splitter 12 to ensure an equal distribution ofincoming randomly polarized light energy into first and secondcomponents having first and second polarizations. Alternatively, thepolarizer 10 can be fixedly mounted at an alternative angle with respectto the beam splitter to provide an alternative intensity ratio. Asanother alternative, the polarizer 10 can be rotatably mounted withrespect to the beam splitter 12 to be selectively adjustable by a userof the emulator 50 to vary the intensity ratio between the first andsecond components A′, A″.

Light energy entering each polarizer 10 travels a path similar to thatshown in FIG. 1 as a result of the arrangement of the beam splitters 12,reflective mirrors/prisms 14, 18, and beam combiners 20, which areoptically aligned to define respective optical paths thereamong, theoptical paths being similar to those shown in FIG. 1.

In the exemplary embodiment of FIGS. 2A–2C, the emulator 50 includesfirst receptacles positioned to pass light energy directed along one ofthe optical paths, i.e. the near vision (S) optical path traveled by thefirst component A′, as illustrated in FIG. 1. Each first receptacle iscapable of receiving an add lens shown in block form at 16 in FIG. 1. Inthe embodiment of FIGS. 2A–2C, the receptacle is provided as a slot 60in the housing 52 for receiving a lens insert functioning as the addlens 16 of FIG. 1.

An exemplary lens insert 70 is shown in FIG. 3. This exemplary lensinsert 70 includes an optical lens 72 providing an add power, a frame 74securing the lens 72, and a handle 76 extending from the frame 74 tofacilitate manual grasping of the lens insert 70 for insertion in andremoval from the slots 60 of the emulator 50. It will be appreciatedthat a set of lens inserts are provided, each having optical lenses of adifferent add power, such that the lens inserts 70 may be usedinterchangeably to apply the desired add power to a viewer's sight path.The slots 60 and lens inserts 70 are configured such that the respectiveoptical lens 72 is optically aligned with light energy traveling thenear vision (S) optical path when the lens insert 70 is properly seatedin the slot 60.

In the exemplary embodiment of FIGS. 2A–2C, each ocular of the emulator50 also includes a second receptacle 80 positioned to pass combinedlight energy traveling along the common optical path Y. Each secondreceptacle 80 is capable of receiving a sphere lens 84 in opticalalignment with light energy traveling the common path. A set ofinterchangeable sphere lenses are provided so that a selected spherelens may be inserted into a selected second receptacle 80 to apply adesired sphere power to a viewer's sight path.

Each ocular of the exemplary emulator 50 also includes a thirdreceptacle 90 provided in position to pass combined light energytraveling along the common optical path Y. Each third receptacle 90 iscapable of receiving a cylindrical lens 94 in optical alignment withlight energy traveling the common path. A plurality of interchangeablecylindrical lenses are provided so that a selected cylindrical lens maybe inserted into a selected third receptacle 90 to apply a desiredcylindrical power to a viewer's sight path, e.g. to corrected forastigmatism. In a preferred embodiment, each second receptacle 80 ispositioned between a respective beam combiner 20 and a respective thirdreceptacle 90, as shown in FIGS. 2A–2C.

The second receptacle 80 is provided to receive a lens functioning asthe sphere lens 22 of FIG. 1. The third receptacle 90 is provided toreceive a lens functioning as the cylindrical lens 24 of FIG. 1. In theexemplary embodiment of FIGS. 2A–2C, each of the second and thirdreceptacles 80, 90 is provided as a respective drop lens holder 96,which includes a respective groove 98 for holding a lens, as best shownin FIGS. 4B and 4C.

Accordingly, a person seeking corrective multifocal contact lenses maybe asked by a health care professional to position his eyes adjacent thefront end 54 of the emulator 50, and to look through the emulator'soculars at a vision chart. The health care provider may repeatedlyinterchange add, sphere and/or cylindrical lenses of each ocular and askthe person to compare visual acuity until an optimal combination oflenses, and thereby a vision prescription, is obtained.

FIGS. 4A–4C are rear, front and cross-sectional perspective views of analternative embodiment of the emulator device 50 of FIGS. 2A–2C. Theoculars of the exemplary emulator 50 of FIGS. 4A–4C are very similar tothose of FIGS. 2A–2C, as best shown in FIG. 4C. However, the housing 52of this exemplary emulator 50 includes a handle 58 so that the person orhealth care professional may easily hold the emulator 50 adjacent theperson's face during development of a vision prescription.Alternatively, the emulator 50 may be configured, e.g. with a mountingbolt, for mounting atop a tripod, etc. In addition, each ocular of thisexemplary emulator 50 includes a wheel 100 capable of supporting severaladd lenses 72. Each add lens provides a respective add power. Each wheel100 is rotatably mounted relative to the beam splitter 12 and/or housing50 for selective positioning of an add lens in the area of the firstreceptacle 60 such that the light energy of the first componenttraveling the S optical path will pass through the selected add lens 72.Such wheels are generally well known in the art of optometry equipment,such as phoropters. Accordingly, a health care professional caninterchange add lenses positioned in the optical path by rotating thewheel 100 to apply an add lens of the desired power to the person'ssight path. This may be achieved by manually rotating the wheel 100 asit is exposed through an aperture 102 in the housing 50. A ball or othertype detent mechanism may be provided to facilitate the alignment of thelenses with the optical path. Various suitable detent mechanisms arewell known in the art.

The exemplary device of FIGS. 4A–4C also includes an interpupillarydistance (IPD) mechanism capable of varying the distance between theoculars of the emulator 50, e.g. between the second and/or thirdreceptacle 80, 90. In other words, the IPD mechanism allows formanipulation of the left eye and right eye oculars of the emulator toalign the common paths exiting the emulator 50, with the pupils of theperson having his vision tested. This is necessary becauseinterpupillary distance varies among individuals. Various IPD mechanismsare generally known in the art for optometry equipment, and any suitableIPD mechanism may be used.

The illustrated IPD mechanism is connected to a convergence mechanism(discussed below) to provide a variable optical path offset that iscapable of keeping the optical path centered on the aperture at variousIPD settings during use of the convergence mechanism. The exemplary IPDmechanism is illustrated with greater detail in FIG. 6. As shown inFIGS. 4A, 4B and 6, the mechanism includes a rotatable knob 120 drivinga pinion 122 rotatably mounted on the housing 52. The pinion 122 isdisposed between parallel racks 124, and has external teeth meshing withteeth of the racks 124. Each rack 124 supports and/or is fixed to arespective left eye or right eye ocular of the emulator 50. Accordingly,rotating the knob 120/pinion 122 in counterclockwise direction separatesthe left eye and right eye oculars of the emulator 50, therebyseparating the portions to accommodate a greater interpupillarydistance, and rotating the knob 120/pinion 122 in a clockwise directioncauses the left and right eye oculars of the emulator 50 to approach oneanother to accommodate a lesser interpupillary distance, as best shownin FIG. 6.

FIG. 5 is a perspective view of an alternative embodiment of theemulator 50 of FIGS. 4A–4C. The oculars and IPD mechanism of theexemplary emulator 50 of FIG. 5 are very similar to those of FIGS.4A–4C. In addition, each ocular of the emulator 50 of FIG. 5 includes aconvergence mechanism capable of pivoting one or both of the left andright oculars of the emulator 50 to cause the left eye and right eyesight paths to intersect at a predetermined reading or near activitydistance. Preferably, the oculars pivot about a fixed point located atthe nominal center of rotation of the eye sockets when the emulator 50is held against the face. This convergence mechanism allows a person tofocus at a point relatively close to the person's face, e.g. in therange of about 12 to 24 inches from the person's face, to simulate acondition in which a person's eyes pivot in their sockets to focus at apoint near the face, e.g. for reading. This allows for testing of visualacuity in a situation simulating reading, which produces a visionprescription for multifocal lenses that will be well-suited to readingor other near vision tasks.

An exemplary convergence mechanism is shown in FIG. 6. As shown in FIG.6, this convergence mechanism includes first and second levers 130, eachof which is pivotably mounted to the housing 52 for movement from afirst position in which the left eye and right eye sight paths aresubstantially parallel (as in FIG. 6), e.g. to simulate a condition inwhich focusing occurs at a significant distance, e.g. greater than abouttwenty (20) feet, to a second position in which the left eye and righteye sight paths intersect (as in FIG. 7), e.g. to simulate a reading orsimilar condition. Generally, this requires pivoting of each ocular inthe range of about 7 to 12 degrees for an interpupillary distance in therange of about 55 to 72 mm for focusing at a range of about 14 to 22inches. Any convergence mechanism capable of pivoting the oculars tocause the left and right eye sight paths to intersect may be used.Preferably, the convergence mechanism causes rotation of the ocularsabout the nominal center of rotation of the human eyes when the emulatoris against the face. The nominal center of rotation of the eyes isapproximately 15 mm behind the anterior surface of the cornea.

FIG. 7 is a schematic diagram illustrating the effect of the convergencemechanism of the device of FIGS. 5 and 6. As will be appreciated fromFIG. 7, light energy passing through the emulator 50 travels alongintersecting sight paths when the left eye and right eye oculars of theemulator 50 are pivoted toward each other to provide the convergenceeffect.

FIG. 8 is a perspective view of another alternative embodiment of theemulator 50 of FIGS. 4A–4C. The oculars and IPD mechanism of theexemplary emulator 50 of FIG. 8 are very similar to those of FIGS.4A–4C. In addition, each ocular of the emulator 50 of FIG. 8 includes asphere adjustment member 140 supporting a plurality of sphere lenses142, 144 of various powers. For example, these sphere lenses maycollectively provide for power adjustment in quarter diopter increments(e.g.+0.50, +0.25, −0.25, −0.50 diopters). Each sphere adjustment member140 is movably supported on the housing 52 to allow selective alignmentof a selected sphere lens 142, 144 with the common optical path for eachrespective eye portion. Preferably, the sphere adjustment member 140also includes a lens-free opening 146, or a plano/0.00 diopter lens,selectively alignable with the common optical path. Although the sphereadjustment member 140 may be provided as a rotatable wheel (not shown),it is preferably provided as a longitudinally translatable elongatedstrip, as shown in FIG. 8.

Accordingly, the sphere lenses of the sphere adjustment members 140 areoptically alignable with the oculars and the second and thirdreceptacles and any sphere and/or cylindrical lenses provided therein,with the respective common optical paths. Accordingly, the sphere lensesof the sphere adjustment members 140 may be used to fine tune a visionprescription by first finding an appropriate sphere lens that ispositioned in the second receptacle/drop holder 96. For example, suchsphere lenses may be provided in 0.50 diopter increments. Then, thesphere adjustment members 140 may be translated to provide adjustmentsto the total applied sphere power in 0.25 diopter increments.Advantageously, this may be performed without the need to remove theemulator 50 from the person's face, or to disrupt the person's viewingof a chart, which is helpful to the person in comparing visual acuitybetween two different applied sphere powers. A ball or other type detentmechanism may be provided to facilitate the alignment of the lenses ofthe sphere adjustment members with the corresponding common opticalpath.

FIG. 9 is a flow diagram 150 illustrating a method for emulating amultifocal contact lens to produce a simultaneous vision effect on aretina of an eye in accordance with the present invention. As shown inFIG. 9, the method begins with splitting of incoming light energy intofirst and second components, as shown at step 152. This involves passingthe incoming light energy through the beam splitter 12, and optionallythe absorption polarizer 10 to create first and second components havingdistinct polarizations, as shown in FIG. 1.

Next, the first component is caused to propagate along a first opticalpath through an add lens, as shown at step 154. The involves directingthe first component along a first optical path. This also may beperformed by the beam splitter 12. In the example of FIG. 1, this alsoinvolves reflecting the light energy of the first component via areflector 14 through the add lens 16.

Additionally, the beam splitter 12 causes the second component topropagate along a second optical path distinct from the first opticalpath, as shown at step 156. Accordingly, this results in passing oflight energy of only the first component through the add lens.

Next, the first and second components of the light energy are recombinedand caused to propagate along a common optical path passing through asphere lens, as shown at steps 158 and 160. This may involve reflectingthe light energy of the first component via a reflector 18 toward a beamcombiner 20 (see FIG. 1). The beam combiner combines the components andcauses them to travel a common optical path through a sphere lens.

Further, the combined light energy is caused to propagate along a commonoptical path passing through a cylindrical lens, and is directed onto aretina of an eye, as shown at steps 162 and 164.

Next, the method involves iteratively interchanging at least one of theadd, sphere and/or cylindrical lenses until a desired level of visualacuity is provided, as shown at steps 166 and 168. This may involveallowing the person to view the eye chart with a first appliedcombination of powers/lenses, allowing the person to view the eye chartwith a second applied combination of powers/lenses, and taking a reportfrom the person as to which combination provides better visual acuity.This may be repeated until a satisfactory or optimal combination isfound. The desired level of acuity may be determined by the person'sperception, an objective guideline, applicable laws, etc., as will beappreciated by those skilled in the art.

When the desired level of visual acuity has been reached, a visionprescription may be prepared to reflect the add, sphere and/orcylindrical powers of the combination of lenses providing the desiredlevel of visual acuity, as shown at step 170. Multifocal contact lensesmeeting that prescription may then be dispensed to the person with ahigh degree of confidence that the dispensed multifocal contact lenseswill provide the desired level of visual acuity.

FIG. 10 is a schematic diagram of another simultaneous vision emulator50 in accordance with the present invention. This emulator 50 operateson a similar principle to that discussed with reference to FIGS. 1–9. Inthe example of FIG. 10, light energy travels in the direction of arrow Band passes through an optional polarizer 160, e.g. a plate absorptionpolarizer, and a trial frame lens 162 that applies a sphere or“distance” power. As discussed above with reference to FIG. 1, thepolarizer 160 can be used to adjust the ratio between components of theincoming light energy that will be directed along the sphere and addpaths after passing through the beamsplitter 164. The light energyexiting the trial frame lens 162 enters a visible waveband polarizingbeamsplitter 164, which produces first and second light energycomponents. A first component (“P” polarization) of the light energygoes straight through the beamsplitter 164 and is sphere only in focallength or “power diopters.” A second component (“S” polarization) of thelight energy is reflected by the beamsplitter 164 through an achromaticquarter waveplate 166 to a mirror 168. The achromatic quarter waveplate166 is oriented relative to the optical path to rotate “S” polarizationto “P” polarization after a double pass through it. The waveplate 166will also rotate “P” polarization to “S” polarization after a doublepass through it. The light energy reflected by the mirror 168 passesback through the achromatic quarter waveplate 166. As a result of thedouble pass of light energy through the waveplate 166, the light energyreentering the beamsplitter 164 has a “P” polarization. As a result ofthis polarization, the light energy passes through the beamsplitter 164and through another achromatic quarter waveplate 170 toward anothermirror 172. This second mirror 172 can be changed or deformed to have aconcave curvature of a varying amount such that the mirror will act asan add lens to apply an add power.

Light energy reflected from the second mirror 172 then passes backthrough the second achromatic quarter waveplate 170. This double pass oflight energy through waveplate 170 causes the light energy reenteringthe beamsplitter 164 to have an “S” polarization again. Because thelight energy now has an “S” polarization, it is reflected by thebeamsplitter 164 towards the eye 26.

It will be appreciated that an achromatic Fresnel rhomb or othercomponent may be substituted for the achromatic quarter waveplate toprovide the quarter shift.

Optionally, a slot for a cylindrical trial frame lens (not shown) tomatch a person's astigmatism may be provided to the left or right of thebeamsplitter 164 as shown in FIG. 10. Alternatively, the lens 160 ispositioned on the right side of the beamsplitter 164, just before theeye 26. As another alternative, either or both mirrors may be curved asdescribed above to separately or cooperatively apply an add power.

Accordingly, in the embodiment of FIG. 10, like the embodiments of FIGS.1–8, incoming light energy is split into a first component directedalong a first optical path S (involving reflection by the mirrors andpassage through the achromatic quarter waveplates), and a secondcomponent directed along a second optical path P distinct from the firstoptical path (involving passage directly through thebeamsplitter/polarization cube 164 of FIG. 10). Additionally, thisembodiment applies an add power to light energy of only the firstcomponent. In this exemplary embodiment, the add power is applied byreflecting the light energy from a curved mirror. Alternatively, an addlens may be used. Furthermore, light energy of the second component, andthe first component after the first component has had the add powerapplied, are directed along a common optical path, namely, toward theretina of the eye.

The combined light energy traveling along the common optical path isalso passed through a sphere lens 162. This may occur before or afterpassage through the beamsplitter 164 (shown before in FIG. 10).Additionally, the combined light energy having the applied add andsphere powers is directed onto the retina of an eye 26 to create thesimultaneous vision effect.

Having thus described particular embodiments of the invention, variousalterations, modifications, and improvements will readily occur to thoseskilled in the art. Such alterations, modifications and improvements asare made obvious by this disclosure are intended to be part of thisdescription though not expressly stated herein, and are intended to bewithin the spirit and scope of the invention. Accordingly, the foregoingdescription is by way of example only, and not limiting. The inventionis limited only as defined in the following claims and equivalentsthereto.

1. A method for emulating a multifocal contact lens to produce asimultaneous vision effect on a retina of an eye, the method comprising:splitting incoming light energy into a first light energy componentdirected along a first optical path, and a second light energy componentdirected along a second optical path distinct from the first opticalpath; applying an add power to only the first component; directing alonga common optical path the second component and the first component afterthe first component has had the add power applied; applying a spherepower to the combined light energy traveling along the common opticalpath; and directing the combined light energy onto a retina of an eyeafter the add and sphere powers have been applied.
 2. The method ofclaim 1, wherein applying the add power comprises: reflecting lightenergy from a beam splitter through an add lens; and reflecting lightenergy from the add lens to a beam combiner.
 3. The method of claim 1,wherein applying the add power comprises: reflecting light energy from acontoured mirror providing an add power.
 4. The method of claim 1,wherein the first optical path includes reflection from a first mirrorfor a double pass through a first achromatic quarter waveplate,transmission through a polarization beamsplitter, and reflection from asecond mirror for a double pass through a second achromatic quarterwaveplate.
 5. The method of claim 1, wherein applying the add powercomprises passing light energy through an add lens, and wherein applyingthe sphere power comprises passing the combined light energy through asphere lens.
 6. The method of claim 5, further comprising: iterativelyinterchanging at least one of the add and sphere lenses until a desiredlevel of visual acuity is provided; and prescribing multifocal contactlenses having add and sphere powers corresponding to respective add andsphere lenses providing the desired level of visual acuity.
 7. Themethod of claim 1, further comprising: applying a cylindrical power tocombined light energy traveling along the common optical path beforedirecting the combined light energy onto the retina of the eye.
 8. Themethod of claim 7, wherein applying the cylindrical power comprisespassing combined light energy through a cylindrical lens.
 9. The methodof claim 8, further comprising: iteratively interchanging at least oneof the add, sphere and cylindrical lenses until a desired level ofvisual acuity is provided; and prescribing multifocal contact lenseshaving add, sphere and cylindrical powers corresponding to respectiveadd, sphere and cylindrical lenses providing the desired level of visualacuity.
 10. The method of claim 1, wherein splitting the incoming lightenergy comprises: passing the incoming light energy through a polarizerto linearly polarize the incoming light energy; and passing thepolarized incoming light energy through a beam splitter to create thefirst and second light energy components directed along the first andsecond optical paths, respectively.
 11. The method of claim 1, whereindirecting the first and second components along a common optical pathcomprises: passing the first and second components through a beamcombiner.
 12. A method for emulating a multifocal contact lens toproduce a simultaneous vision effect on a retina of an eye, the methodcomprising: splitting incoming light energy into first component andsecond components; applying an add power the first component, applying asphere power to the second component and the first component after thefirst component has had the add power applied; and directing the firstand second components, after having had the add and sphere powersapplied, onto a retina of an eye.
 13. The method of claim 2, furthercomprising: using a first lens to apply one of the add and spherepowers; replacing the first lens with a second lens having a powerdifferent from the first lens; and receiving a report from a personcomparing visual acuity with the first and second lenses, respectively.